Rosberg’s fastest lap, in a session that saw track temperatures drop from 33 degrees celsius on a bright and breezy afternoon to a balmy 25 after dark, was 0.365 slower than his British team mate.

Ferrari’s Fernando Alonso was third fastest in both sessions, with Red Bull’s Daniel Ricciardo fourth in the evening and Force India’s Nico Hulkenberg filling that spot in the afternoon.

Ricciardo again suffered problems with his car’s fuel flow sensor, the same part that has failed in both of the first two races of the season.

McLaren’s Jenson Button, the 2009 world champion who will be starting his 250th race on Sunday, was fifth and sixth in the respective sessions.

The timesheets reinforced Mercedes’ early-season superiority, with four cars powered by their engines in the top five after lunch.

Williams, who also have Mercedes engines, had Brazilian Felipe Massa fifth in the evening session despite sitting out the first half of the session because they already had plenty of data from eight days of pre-season testing in Bahrain.

Alonso provided some surprise when Ferrari accidentally sent him out with one soft tyre and three mediums on his car in the first session. The Spaniard stopped in the pit lane and was pushed back.

Three reserve drivers made debut appearances for the season in first practice, with Brazilian Felipe Nasr given track time at Williams, Dutchman Giedo van der Garde at Sauber and compatriot Robin Frijns at Caterham.

The sessions were untroubled by any protests elsewhere against the race, the country’s biggest annual sporting event and a prestige project for the ruling monarchy.

Bahrain has suffered sporadic unrest since an uprising led by its Shi’ite Muslim community in early 2011 demanding reforms and a bigger share of power in the Sunni-led government.

Anti-government demonstrators threw petrol bombs and clashed with police, who fired tear gas and birdshot, after a funeral procession on Thursday night in a Shi’ite village south of the capital Manama.